Multimode discone antenna

ABSTRACT

A turnstile antenna includes four arms disposed concentric of a vertical axis and orthogonally related to each other so that diagonally related arms form a dipole. The four arms are physically and electrically coupled to a circular member disposed coaxially of the vertical axis. The four arms extend downward at an angle less than 90* with respect to the vertical axis. The pair of dipoles have a first energy coupling arrangement for orthogonal energy coupled to adjacent orthogonal arms to provide right and left hand circularly polarized omnidirectional patterns. A cylinder disposed coaxially of the vertical axis and spaced from the circular member extends through the turnstile antenna to support a disc therefrom in a perpendicular relation to the vertical axis and above the turnstile antenna. A second energy coupling arrangement for inphase energy is coupled to the disc and diagonally disposed arms of the turnstile antenna. The thusly formed combination provides a discone antenna having a vertically polarized omnidirectional pattern. Two variations of both the first and second energy coupling arrangements are disclosed.

United States Patent 1191 Spanos June 26, 1973 MULTIMODE DISCONE ANTENNA [75] Inventor: William M. Spanos, Wayne, NJ.

[73] Assignee: International Telephone and Telegraph Corporation, Nutley, NJ.

22 Filed: Feb. 12, 1971 21 Appl. No.: 105,884

521 u.s.c1 343/730,343/773,343/797,

V W V 7 343/854 51 1m. c1. H01q 1/00 [58] FieldofSearch 343/727, 730, 773, 343/797, 847, 854

[56] References Cited UNITED STATES PATENTS 3,579,244 5/1971 Dempsey 343/797 Primary ExaminerEli Lieberman Attorney C. Cornell Remsen, Jr., Walter J. Baum, Paul W. Hemminger, Charles L. Johnson, Jr., Philip M. Bolton, Isidore Togut, Edward Goldberg and Menotti J. Lombardi, Jr.

3 mar vearl [57] ABSTRACT A tumstile antenna includes four arms disposed concentric of a vertical axis and orthogonally related to each other so that diagonally related arms form a dipole. The four arms are physically and electrically coupled to a circular member disposed coaxially of the vertical axis. The four arms extend downward at an angle less than 90 with respect to the vertical axis. The pair of dipoles have a first energy coupling arrangement for orthogonal energy coupled to adjacent orthogonal 7 arms to provide right and left hand circularly polarized omnidirectional patterns. A cylinder disposed coaxially of the vertical axis and spaced from the circular member extends through the tumstile antenna to support a disc therefrom in a perpendicular relation to the vertical axis and above the tumstile antenna. A second energy coupling arrangement for inphase energy is coupled to the disc and diagonally disposed arms of the tumstile antenna. The thusly formed combination provides a discone antenna having a vertically polarized omnidirectional pattern. Two variations of both the first and second energy coupling arrangements are disclosed.

10 Claims, 5 Drawing Figures LLY OR IEFTHAND POLA IZEU C IRCULQRl-Y OHNINREUIONAL POLARI ED ENERGY OHNIDIRECTIONAL ENERGY Patented June 26 1973 2 Sheets-Sheet 1 INVENTOR WILL 1AM v M. SPA/V05 AGENT 2 Sheets-Sheet 2 14 LEFT HAND R GHT HAND VER ICALLY CIRCULARLY CIRCULARLY POLARIZED POLARIZED POLARIZED OHN ECTIONAL OHMMRECTIWL OHNINRKIIONAL 0 RT PORT PORT 17 [////////4 /////////////////////l Z241 i 1T 22' i 6 I mum -i L Poumeo I A I I Z OMNIDIRECTIONAL f 9 f eueacv z I g 20' 4 samurow \U DIVIDER on ADDER R Y INVENTOR S LEQ WILLIAM M, SPANOS OMNIDIRECTIONAL BY ENERGY AGENT 1 MULTIMODE DISCONE ANTENNA BACKGROUND OF THE INVENTION This invention relates to antennas and more particularly to multimode antennas.

Because of existing space limiations and a need for greater numbers of antennas to provide radiating means for a multiplicity of services, the trend in antenna design is toward compact multipurpose radiators which provide more than one function. For example, in mobile applications, requirements exist for providing radio communications and navigation functions simultaneously in either different frequency bands, or in the same frequency band. The antenna radiation characteristics with respect to pattern coverage and polarization are not necessarily identical. The advent of communication and navigation systems which utilize satellites have greatly complicated the design of common multipurpose antennas because of requirements for pattern coverage and polarization which differ from those for line-of-sight (LOS) ground-to-ground and ground-to-air links. The satellite systems require circular polarization and overhead coverage from ground base antennas, necessitating different modes of excitation in the antenna from those used for conventional systems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multimode antenna suitable for utilization in satellite systems.

Another object of the present invention is to provide a multimode antenna capable of having simultaneously a vertically polarized omnidirectional pattern, a right hand circularly polarized omnidirectional pattern and a left hand circularly polarized omnidirectional pattern.

Still another object of the present invention is to provide a multimode antenna capable of utilization with satellite systems, LOS communication systems and/or navigation systems.

A feature of the present invention is the provision of a multimode antenna capable of having simultaneously a vertically polarized omnidirectional pattern, a right hand circularly polarized omnidirectional pattern and a left hand circularly polarized ommidirectional pattern comprising a turnstile antenna having four arms disposed orthogonally about a vertical axis, portions of the arms extending downward at a given angle less than 90 with respect to the vertical axis, diagonally related ones of the arms forming a dipole, a circular member disposed coaxially of the vertical axis to physically and electrically interconnect the arms, and a first energy coupling means coupled to orthogonally related adjacent ones of the arms to feed orthogonal energy to and remove orthogonal energy from the turnstile antenna; a disc disposed in perpendicular relation to the vertical axis; first means to physically'support the disc above the turnstile antenna; and an second energy coupling means coupled to diagonally related ones of the arms.

and the disc to feed inphase energy to and remove inphase energy from a discone antenna formed by the disc and the arms.

BRIEF DESCRIPTION OF THE DRAWING Above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross sectional view of the multimode antenna and one embodiment of its feed arrangement in accordance with the principles of the present invention;

FIG. 2 is a cross sectional view of FIG. 1 taken along line 22 of FIG. 1;

FIG. 3 is a bottom plan view of FIG. 1 taken along line 33 of FIG. 1 and a schematic illustration of the manner energy is fed to the multimode antenna in ac cordance with the principles of this invention;

FIG. 4 is a cross sectional view partially in elevation of the multimode antenna and an alternative feed arrangement in accordance with the principles of the present invention; and

FIGIS is a cross sectional view of FIG. 4 taken along line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For purposes of explanation, let us consider a UHF (ultra high frequency) LOS ground-to-ground communication; UHF satellite communications and L-band DME (distance measuring equipment)/Tacan or RSB (Radar Safety Beacon)/IFF (Identification Friend or Foe) applications wherein the following requirements would exist for an antenna at a user station.

Function Polarization Frequency Band Pattern Coverage UHF LOS Vertical 225-400 MHZ Figure 8 in Communications elevation, omnidirectional UHF Dual Circular 225-400 MHZ Satellite hemispherical Communication DME/TacanNenical 960- l2l5 MHZ Figure 8 in RSB/IFF elevation,

omnidirectional The term dual circular as presented in the above table refers to right and left hand circularly polarized radiation. The term hemispherical presented in the above table has reference to a right and left hand circularly polarized omnidirectional pattern.

Referring to FIGS. 1, 2 and 3, there is disclosed therein one embodiment of a multimode antenna in accordance with the principles of the present invention.

a Right and left hand circularly polarized omnidirecorthogonal energy to and remove orthogonal'energy.

from the thusly formed turnstile antenna.

More specifically the first energy coupling means ineluding coaxial lines 6 and 7 each have afirst portion 8 extending upwardly towards arms 1 and 4,-respectively, substantially parallel to cylinder9 and a second portion 10 coupled to and extending-at substantially right angles to portion 8 within arms 1 and 4, the center conductor 11 of portion 10 being electrically conneeted to circular'member 5;

Circular member 5 may be used in common by the orthogonally related dipoles for feeding energy thereto because of the manner in which the current provided by the energy from the coaxial lines 6 and 7 flow in the circular member 5 and the arms 1-4. For instance, in FIG. 2 note the solid arrows indicating the current i when energy is coupled through coaxial line 6 to the dipole or received from the dipole by coaxial lines 6. At the coupling point between center conductor 11 and member 5, the current i divides into two parts in member 5 having a value of i/2. These currents are conducted out both arms 2 and 4 and back down arms 2 and 4 so that there is equal and opposite current magnitude which cancel one another. The current then proceeds around member 5 to arm 3 so that the current is algebraically combined and produces a single current vector i in arm 3. Now let us consider the energy coupled from or to coaxial line 7. This current iis shown by the dotted arrows. As before the current i divides into two paths at the junction between center conductor 11' and number 5 and proceeds out and back on arms 1 and 3 such that the magnitudes will be equal and in opposite directions which cancel one another. The resultant current then proceeds to arm 2 where it is algebraically combined. It is obvious from the foregoing that the common member 5 can be employed to feed energy to the orthogonally related dipoles of the turnstile antenna without interference between each other and thereby provide the desired left and right hand circularly polarized omnidirectional radiation pattern provided the energy is appropriately coupled from quadrature hybrid 12 whose input terminal 13 and 14 are excited by left and right hand circularly polarized energy respectively. The input and output from the ports 15 and 16 illustrate the left hand circularly polarized orthogonal relationship by the symbols 0 and 90 while the right hand circularly polarized orthogonal energy is represented by the symbols (90) and (0).

It should be noted that the portion of the arms 1-4 that extend downward at an angle less than 90 with respect to the vertical axis have a length greater than one quarter wavelength at the operating frequency of the turnstile antenna. The purpose of this angular relationship is to permit the utilization of the arms 1-4 of the turnstile antenna to simulate a cone which in conjunction with disc 17 forms a discone antenna to provide the desired vertically polarized omnidirectional antenna pattern.

Cylinder 9 supports at its top end thereof disc 17 so as to be disposed above the turnstile antenna. Energy is coupled to the discone antenna by means of a coaxial line 18 extending coaxially of the vertical axis and throughcylinder 9 to a shunt power divider or adder 19. Coaxial line 18 has a characteristic impedance of 50 ohms and the coaxial lines and 21 extending from divider or adder 19 have a I00 ohm characteristic impedance. Coaxial line 20 and 21 also have a length of one quarter wavelength at the operating frequency of the turnstile antenna to provide an open circuit across dipole members 1 and 2. As illustrated the center conductor 22 of coaxial line 20 and the center conductor 23 of coaxial line 21 extends through disc 17 at the appropriate points to make electrical contact with arms 1 and 3 of the turnstile antenna thereby providing a feed point for the discone antenna formed by arms 1-4 s of the turnstile antenna and disc 17. The energy coupled to or from the discone antenna is inphase energy to provide the vertically polarized omnidirectional pat tern. Due to the inphase excitation of the discone antenna cylinder 9 will be excited. To prevent the excitation of cylinder 9 from distorting the radiation pattern bars 24 and 24' are coupled between the outer wall of cylinder 9 and the outer conductor of coaxial lines 6 and 7 at a distance of one quarter wavelength at the operated frequency of the discone antenna below arms 1 and 4 to provide a quarter wave choke for the radio frequency (RF) energy exciting the cylinder 9 and thereby short circuit this energy to prevent pattern distortion. The structure of this RF choke is completed by providing bars 25 and 26 coupled to arm 3 and the outer surface of cylinder 9 and bars 27 and 28 coupled to arm 2 and the outer surface of cylinder 9. Bars 26 and 28 are disposed one quarter wavelength at the operating frequency of the discone antenna from their associated arms 3 and 2.

As illustrated in FIG. 1, the diameter of the lower end portion of diagonally related arms, such as arms 1 and 3, has a dimension that is greater than one quarter wavelength at the operating frequency and identified as dimension D. On the other hand disc 17 has a diameter that is less than one quarter wavelength at the operating frequency and is related to dimension D by approximately 0.7 D.

Divider or adder 19 and coaxial cables 20 and 21 cooperate to provide an open circuit at the discone feed points with respect to the orthogonal or balanced excitation of the turnstile antenna signal thereby preventing interaction. The use of the dual ohm characteristic impedance coaxial lines 20 and 21 eliminate the need for an impedance transformer. Coaxial cables 20 and 21 and divider or adder 19 disposed above disc 17 are kept as close to the disc as possible to avoid affecting radiation pattern.

FIGS. 4 and 5 illustrate an alternative arrangement of the first and second feeding arrangements of FIG. 1. Like components in FIGS. 4 and will given the same reference characters as in FIGS. 1-4. In the arrangement of FIGS. 4 and 5, the right and left hand circularly polarized omnidirectional pattern is provided by having a feed arrangement for the turnstile antenna coupled within and through arms 1 and 4 with their inner conductors extending to circular member 5.

The inphase energy feed arrangement for the discone antenna formed by disc 17 and arms 1-4 is provided by a 50 ohm coaxial line 18', shunt power divider or adder 19, and coaxial lines 20' and 21 extend from the power divider 19 so as to be in electrical contact with arms 1 and 3 with their inner conductors 22' and 23' extending to disc 19 to provide the feed point for the discone antenna. Bars 29 and 30 disposed a quarter wavelength at the operating frequency below arms 1 and 3 are coupled between the outer surface of cylinder 9 and the outer conductor of coaxial lines 20 and 21, respectively, to provide a portion of the RF choke for energy present on cylinder 9. The other portion of the RF choke is provided by bars 31 and 32 extending downward from arms 2 and 4 and the bars'33 and 34 disposed one quarter wavelength at the operating frequency below arms 2 and 4 so as to be in contact with bars 31 and 32 and the outer surface of cylinder 9.

In all other regards the antenna and the energy feeding arrangement of FIGS. 4 and 5 will operate as described with respect to FIG. 1, 2 and 3 hereinabove. The only difference is the removing the feed arrangement from the top of disc 17 to assure there is no radiation pattern distortion and to accommodate this feed arrangement to rearrange the feed arrangement for the turnstile antenna.

While l have described above the principles of my invention in connection with specific apparatus it is to be more clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A multimode antenna capable of having simultaneously a vertically polarized ommidirectional pattern, a right hand circularly polarized omnidirectional pattern and a left hand circularly polarized omnidirectional pattern comprising: a turnstile antenna having four arms disposed orthogonally about a vertical axis, portions of said arms extending downward at a given angle less than 90 with respect to said vertical axis, diagonally related ones of said arms forming a dipole,

a circular member disposed coaxially of said vertical axis to physically and electrically interconnect said arms, and

first energy coupling means coupled to orthogonally related adjacent ones of said arms to feed orthogonal energy to and remove orthogonal energy from said turnstile antenna;

a disc disposed in perpendicular relation to said vertical axis; first means to physically support said disc above said turnstile antenna; and

second energy coupling means coupled to diagonally related ones of said arms and said disc to feed inphase energy to and remove inphase energy from a discone antenna formed by said disc and said arms. I

2. An antenna according to claim 1, wherein said first means includes a cylinder disposed coaxially of said vertical axis and spaced from said circular member.

3. An antenna according to claim 2, wherein said second energy coupling means includes a first coaxial line disposed coaxially of and extending through said cylinder to a given point above said disc,

power divider means coupled to said first coaxial line at said given point,

a second coaxial line coupled to said power divider means and extending to a first point on said disc adjacent one of said diagonally related ones of said anns, the center conductor of said second coaxial line extending through said disc at said first point and making electrical contact with said one of said diagonally related ones of said arms, and

a third coaxial line coupled to said power divider means and extending to a second point on said disc adjacent the other of said diagonally related ones of said arms, the center conductor of said third coaxial line extending through said disc at said second point and making electrical contact with said other of said diagonally related ones of said arms.

4. An antenna according to claim 3, wherein said first coaxial line has a 50 ohm characteristic impedance;

said power divide means is a shunt power divider; said second coaxial line has a ohm characteristic impedance and a length of one quarter wavelength at the operating frequency of said discone antenna; and said third coaxial line has a 100 ohm characteristic impedance and a length of one quarter wavelength at the operating frequency of said discon'e antenna. 5. An antenna according to claim 2, wherein said second energy coupling means includes a first coaxial line disposed below said turnstile antenna, power divider means coupled to said first coaxial line below said turnstile antenna,

a secondcoaxial line coupled to said power divider means and extending upward substantially parallel to said cylinder to one of said diagonally related ones of said arms, the center conductor of said second coaxial line extending through said one of said diagonally related ones of said arms and making electrical contact with said disc, and a third coaxial line coupled to said power divider means and extending upward substantially parallel to said cylinder to the other of said diagonally related ones of said arms, the center conductor of said third coaxial line extending through said other of said diagonally related ones of said arms and making electrical contact with said disc. 6. An antenna according to claim 5, wherein said first coaxial line has a 50 ohm characteristic impedance; said power divider means is a shunt power divider; said second coaxial line has a 100 ohm characteristic impedance and a length of three quarter wavelength at the operating frequency of said discone antenna; and said third coaxial line has a 100 ohm characteristic impedance and a length of three quarter wavelength at the operating frequency of said discone antenna. 7. An antenna according to claim 5, further including at least a first member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said second coaxial line, and a second member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said third coaxial line, said first and second members providing at least a part of a one quarter wavelength choke for energy on said cylinder at the operating frequency of said discone antenna. 8. An antenna according to claim 2, wherein said first energy coupling means includes a first coaxial line having a first portion extending upward toward one of said orthogonally related adjacent ones of said arms substantially parallel to said cylinder, and a second portion coupled to and extending at substantially right angles to said first portion within said one of said orthogonally related adjacent ones of said arms, the center conductor of said second portion being electrically connected to said circular member; and a second coaxial line having a third portion extending upward toward the other of said orthogonally related adjacent ones of said arms substantially parallel to said cylinder, and a fourth portion coupled to and extending at substantially right angles to said third portion within said other of said orthogonally related adjacent ones of said arms, the center conductor of said fourth portion being electrically connected to said circular member. 9. An antenna according to claim 8, further including at least a first member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor. of said first portion, and a second member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said third portion, said first and second members providing at least a part of a one quarter wavelength choke for energy on said cylinder at the operating frequency of said discone antenna. 10. An antenna according to claim 1, wherein said first energy coupling means includes a first coaxial line extending within and through one of said orthogonally related adjacent ones of said arms, the center conductor of said first coaxial line being electrically connected to said circular member, and a second coaxial line extending within and through the other of said orthogonally related adjacent ones of said arms, the center conductor of said second coaxial line being electrically connected to said circular member. 

1. A multimode antenna capable of having simultaneously a vertically polarized ommidirectional pattern, a right hand circularly polarized omnidirecTional pattern and a left hand circularly polarized omnidirectional pattern comprising: a turnstile antenna having four arms disposed orthogonally about a vertical axis, portions of said arms extending downward at a given angle less than 90* with respect to said vertical axis, diagonally related ones of said arms forming a dipole, a circular member disposed coaxially of said vertical axis to physically and electrically interconnect said arms, and first energy coupling means coupled to orthogonally related adjacent ones of said arms to feed orthogonal energy to and remove orthogonal energy from said turnstile antenna; a disc disposed in perpendicular relation to said vertical axis; first means to physically support said disc above said turnstile antenna; and second energy coupling means coupled to diagonally related ones of said arms and said disc to feed inphase energy to and remove inphase energy from a discone antenna formed by said disc and said arms.
 2. An antenna according to claim 1, wherein said first means includes a cylinder disposed coaxially of said vertical axis and spaced from said circular member.
 3. An antenna according to claim 2, wherein said second energy coupling means includes a first coaxial line disposed coaxially of and extending through said cylinder to a given point above said disc, power divider means coupled to said first coaxial line at said given point, a second coaxial line coupled to said power divider means and extending to a first point on said disc adjacent one of said diagonally related ones of said arms, the center conductor of said second coaxial line extending through said disc at said first point and making electrical contact with said one of said diagonally related ones of said arms, and a third coaxial line coupled to said power divider means and extending to a second point on said disc adjacent the other of said diagonally related ones of said arms, the center conductor of said third coaxial line extending through said disc at said second point and making electrical contact with said other of said diagonally related ones of said arms.
 4. An antenna according to claim 3, wherein said first coaxial line has a 50 ohm characteristic impedance; said power divide means is a shunt power divider; said second coaxial line has a 100 ohm characteristic impedance and a length of one quarter wavelength at the operating frequency of said discone antenna; and said third coaxial line has a 100 ohm characteristic impedance and a length of one quarter wavelength at the operating frequency of said discone antenna.
 5. An antenna according to claim 2, wherein said second energy coupling means includes a first coaxial line disposed below said turnstile antenna, power divider means coupled to said first coaxial line below said turnstile antenna, a second coaxial line coupled to said power divider means and extending upward substantially parallel to said cylinder to one of said diagonally related ones of said arms, the center conductor of said second coaxial line extending through said one of said diagonally related ones of said arms and making electrical contact with said disc, and a third coaxial line coupled to said power divider means and extending upward substantially parallel to said cylinder to the other of said diagonally related ones of said arms, the center conductor of said third coaxial line extending through said other of said diagonally related ones of said arms and making electrical contact with said disc.
 6. An antenna according to claim 5, wherein said first coaxial line has a 50 ohm characteristic impedance; said power divider means is a shunt power divider; said second coaxial line has a 100 ohm characteristic impedance and a length of three quarter wavelength at the operating frequency of said discone antenna; and said third coaxial line has a 100 ohm charActeristic impedance and a length of three quarter wavelength at the operating frequency of said discone antenna.
 7. An antenna according to claim 5, further including at least a first member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said second coaxial line, and a second member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said third coaxial line, said first and second members providing at least a part of a one quarter wavelength choke for energy on said cylinder at the operating frequency of said discone antenna.
 8. An antenna according to claim 2, wherein said first energy coupling means includes a first coaxial line having a first portion extending upward toward one of said orthogonally related adjacent ones of said arms substantially parallel to said cylinder, and a second portion coupled to and extending at substantially right angles to said first portion within said one of said orthogonally related adjacent ones of said arms, the center conductor of said second portion being electrically connected to said circular member; and a second coaxial line having a third portion extending upward toward the other of said orthogonally related adjacent ones of said arms substantially parallel to said cylinder, and a fourth portion coupled to and extending at substantially right angles to said third portion within said other of said orthogonally related adjacent ones of said arms, the center conductor of said fourth portion being electrically connected to said circular member.
 9. An antenna according to claim 8, further including at least a first member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said first portion, and a second member disposed one quarter wavelength at the operating frequency of said discone antenna below said turnstile antenna electrically connecting said cylinder and the outer conductor of said third portion, said first and second members providing at least a part of a one quarter wavelength choke for energy on said cylinder at the operating frequency of said discone antenna.
 10. An antenna according to claim 1, wherein said first energy coupling means includes a first coaxial line extending within and through one of said orthogonally related adjacent ones of said arms, the center conductor of said first coaxial line being electrically connected to said circular member, and a second coaxial line extending within and through the other of said orthogonally related adjacent ones of said arms, the center conductor of said second coaxial line being electrically connected to said circular member. 